On Sunday, 7 September, all of South Africa will be able to see a total eclipse of the Moon (weather permitting, of course). Here in Port Alfred and surrounding areas the eclipse will occur as the full Moon is rising in the east just after sunset.
Eclipses of the Sun and Moon typically happen twice per year. While half the world gets to see each lunar eclipse, for a solar eclipse you have to be in just the right spot to see totality.
A solar eclipse happens when the Moon passes in front of the Sun and its shadow is cast on the ground, moving at over 1600 km/h. The shadow is about 140km wide, so only those standing in the pathway of the shadow get to see a total eclipse of the Sun.
For a lunar eclipse, however, the Moon passes through the Earth’s shadow, so anyone on the side of the Earth where the Moon is up can see the eclipse. More than half the world’s population will be able to see this Sunday’s eclipse, with it being at moonrise for us in South Africa, and at moonset for those over in the far east of Australia.
A lunar eclipse can only occur at full Moon, which is when the Moon is opposite the Sun in the sky, so the Moon passes into the Earth’s shadow. Since the Sun and Moon are opposite each other, moonrise occurs at sunset. This is true for every full Moon.
On Sunday evening, 7 September, the Sun will set and the Moon will rise (for a flat horizon, such as over the sea) just before 6pm here in Port Alfred. Elsewhere in South Africa moonrise and sunset times vary slightly from east to west, but the times of the eclipse are the same across the country.
The Moon will be essentially due east at the time of the eclipse. As the Moon moves into the Earth’s shadow, you will see a small semi-circle of shadow on the Moon beginning at 6.27pm, the start of the partial phase of the eclipse.
The Moon will be fully into the Earth’s shadow from 19:30:48 to 20:52:51, so total eclipse will last 1 hour and 22 minutes. Maximum eclipse at 20:12 may be when the Moon is most beautiful. This is when it will be the deepest red – the so-called “Blood Moon”. Following 20:53 the Moon will again be partially eclipsed for another hour until 21:56:31.
The Moon shines by reflected sunlight, so you might think that when the full Moon passes into the Earth’s shadow, the Moon would go dark and not be visible. But that is not the case. As sunlight enters the Earth’s atmosphere, it is refracted by the air – that is, the path of the light is bent inwards. That means that some of the light is refracted into the Earth’s shadow to dimly light up the eclipsed full Moon.
The atmosphere scatters blue light away. That is why the sky is blue. Red light can penetrate better, and that is why sunsets are red. The red light passes through the air and the blue light is scattered away.
During the lunar eclipse it is primarily the red light that is refracted into the shadow, so the eclipsed Moon will have a reddish glow – the Blood Moon. This is a great spectacle, and an opportunity for beautiful photographs, especially with a carefully chosen scenic foreground.
Just how red the Moon will appear will depend on the conditions in the atmosphere around the rim of the Earth (as seen from the Moon) where the relevant refraction is taking place. With many wildfires currently burning around the world, it may be that the smoke will cause a particularly red Moon, just as smoke, haze, or (unfortunately) pollution can cause a very red sunset.
The reason that there is not a lunar eclipse every full Moon is that the Moon’s orbit about the Earth is tilted by 5 degrees to the Earth’s orbit around the Sun. So, most months the Moon passes either above or below the Earth’s shadow at full Moon and there is no eclipse. But twice per year, 6 months apart, the Moon is passing through the Earth’s orbit at the time of full Moon and there is a lunar eclipse.
Not all of the lunar eclipses are total, and for each one only one hemisphere of the Earth gets to see the eclipse. As a result, the next total lunar eclipse that will be fully visible from Port Alfred will not be until 20-21 December 2029.
So, don’t miss this one!
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Donald Kurtz is Extraordinary Professor at North-West University in Mahikeng. He has an A-1 rating from the South African National Research Foundation, its highest rating. He also holds appointments in the UK of Emeritus Professor at the University of Central Lancashire and Visiting Professor of Astrophysics at the University of Lincoln. He was previously Professor of Astronomy at the University of Cape Town, where he worked for 24 years. Don has over 500 professional publications and was awarded the 2022 Service Award of the Royal Astronomical Society for a lifetime of public outreach and for his service on many international committees.
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This article was first published in Talk of the Town, September 4, 2025. The newspaper serving the communities of Ndlambe and the Sunshine Coast, with a weekly wrap of Makhanda news, is available at stores from early on Thursdays
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